Top

Cabin Heating & Cooling Systems

Introduction:

  • Cabin heat is the system used to condition the air for the pilot and passenger's comfort during colder months and higher altitudes
  • There are two main systems:
Heat Exchanger
Heat Exchanger
Heat Exchanger
Heat Exchanger

Heat Exchanger:

  • Inlet air is bypassed through an exhaust shroud
  • Air is ducted from exhaust shroud, now heated, into ventilation ducts inside of the cabin [Figure 1]
Hartzell Combustion Heater Assembly
Hartzell Combustion Heater Assembly
Hartzell Combustion Heater Assembly
Hartzell Combustion Heater Assembly

Combustion Heater:

  • Uses fuel from the aircraft fuel system to support a flame in a designated heater unit
  • Air enters the combustion chamber by use of a fan or ram air where it is then burned inside a shroud [Figure 2]
  • The resulting warm air from the shroud is routed into the cabin while the exhaust gas is vented overboard
  • Heat is regulated with a thermostat

Cabin Heat Malfunctions:

  • Exhaust pipes may burst allowing carbon monoxide to enter the cabin
  • Heaters may have the same problem with the internal combustor

Common Training Aircraft Heating and Cooling Characteristics:

  • Cessna 172:

    • Temperature and intensity adjusted with push-pull labeled CABIN HT and CABIN AIR
    • Air enters from wing and nose inlet vents
    • Air heated with a heat exchanger with a shroud over exhaust pipes
  • Piper Arrow:

    • Temperature and intensity adjusted with sliders
    • Air enters from wing and nose inlet vents
    • Air is heated with a heat exchanger with a shroud over exhaust pipes
    • Additional air enters from the aft fuselage

Conclusion:

  • Carbon Monoxide Poisoning in a silent killer who's risk can be mitigated through a few simple steps
  • Especially in winter months, refresh your knowledge on Carbon Monoxide and conduct an extra thorough preflight
    • Remember, the heater system may have gone unused for months
  • You can find more information about your aircraft in Chapter 7 of the Pilot Operating Handbook

References: